Lightning-arrester



(1. LE G. FORTESCUE LIGHTNING ARRESTER. APPLICATION FILED MAR. 14. 119 17 Patented July 29, 1919.

IIIIIIIIIIIllIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII WITNESSES INVENTOR Char/ea LeG fJr/zacae ATTORNEY UNITED STATES PATENT OFFICE.

CHARLES LE G. FOBTESCUE, 0]! PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRIC 6t MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

LIGHTNING-ARRESTED.

Specification or Letters Patent.

Patented July 29, 1919.

To all whom it may concern:

Be it known that 1, CHARLES LE G. Fon'rasoUn, a subject of the King of England, and a resident of Pittsburgh in the county of Allegheny and State 0 Fennsylvania, ave invented a new and useful Improvement in Lightnin -Arresters, of which the following is a speci cation.

My invention relates to devices for pro tecting electrical circuits and the 'ap aratus associated therewith from abnorma highpotential stresses, such as may be occasioned by lightning discharges, static disturbances and the like.

More particularly, my invention relates to lightning arresters that are adapted to be dlrectly inserted in transmission line conductors and are devoid of ground connections or discharge paths to ground, thereby eliminating the danger that arises when the dynamo currents tend to flow to ground in the paths initially established by the discharge of the high-frequency or'high-potential impulses.

For the protection of transmission lines o eratin at'high voltages, it is desirable to a sorb t e energy of disturbances by employing protective devices which are devoid of ground connections because ground connections impair the insulating pro erties of the transmission conductors as we as those of the electrical apparatus connected in circuit. Moreover, danger frequently arises by havin ground connections because of the possibility of the arcing grounds having critical frequencies. that may tend to establish resonant conditions in the circuits.

It has been proposed to employ energyabsorbing devices which shall be direct y connected in circuit with the transmission line conductors and shall comprise choke coils that will permit the line currents of normal frequency to ass therethrough without substantial impe ance, and resistorsconnected in shunt to the choke coils that shall absorb the energy of such disturbances as may be directed therethrou'gh by reason of the inductive impedance presented by the choke'coils. Lightning arresters of this general character are set forth inU. S. Patent No. 1,034,197 and U. S. Patent No. 1,217,453.

In the latter patent, the protective device comprises a choke coil and energy-absorbing means associated therewith. The electrical equivalent of this device may be reprehad to the following description and the accompanying drawing in which Figure 1 is a view, artlally in section and partially in side ovation, of a protective device constructed in accordance with my invention; Fi 2 is a diagram illustratin the electrica equivalent for the device 0 Fig. 1, and Fig. 3 is another diagram that illustrates the electrical equivalent of the device of Fig. 1, under certain'conditions.

Referring to Fig. 1, a choke coil 1 made in any form and of a film-forming metal, preferablyaluminum, is immersed in a body of electrolyte 2 that iscontained in a tank 3. The tank 3 is mounted upon insulating supports 4 and is provided with a cover 5 through which leads 6 of the choke coil 1 project. Terminals 7 of the leads 6 provide means for connecting a line conductor 8 to the protective device. The choke coil 1 is, therefore, directly inserted in circuit with the line conductor 8 and is adequately insulated from ground, thereby precluding any current from'flowing to ground.

The electrolyte 2 possesses the property of forming a high-resistance film of high s ecific inductive ca acit upon the exte or surface of the cho e 0011 1 which, under 'ordinary conditions, suifices to confine the line currents o the choke coil. When disturbances or high-requeney impulsesv impinge upon the coil 1 the resultant potential stress occasioned bythe inductive reactance offered by the coil is suflicient to disrupt this resistance film A. non-inductive path is consequently provided for the flow of the disturbance through the body of the electrolyte which serves as a resistor to absorb the energy of the disturbance. y

o more fully understand the operation of my rotective derice, reference may be had to ig. 2 in which a structure is die grammatically illustrated that is the electrical equivalent of the device of Fig. 1. In

Fig. 2, an inductance coil 9 may represent the coil 1 of Fig. 1. Resistance elements 10 and condensive elements 11 are connected in shunt to the convolutions of the coil 9, as shown. The condensive elementsll represent, diagrammatically, the electrostatic capacity that is imparted by the films and developed between adjacent convolutions of the coil 1 when very high-frequenc impulses are impressed upon the 0011. T e resistors 10, shunting the condensers 11, re resent the resistance of the discharge pat 5 through the body of electrolyte between adjacent convolutions of the coil. As the'frequency of the impulses impressed upon the coil 9 increases, the resultant potentials exert a greater and greater electrical pressure upon the separate convolutions of the coil. As a result, larger and larger quantities of energy are forced to flow through the resistors 10 and the condensers 11 by reason of the 'decreasin resistance offered by the resistance films ormed upon the coil. In this manner, the energy forced to flow through the elements 10 and 11 is dissipated as heat.

The device of Fig. 2 is selective for alternating currents of an."frequency; that is, a circuit comprising t e proper amount of inductivereactance and condensive reactanoe to constitute a parallel'resonant circuit for a certain fre uency will be selected by im ulses of that requency. These impulses wi l consequently cause circulating currents of the same frequency to flow in the selected resonant circuits thus established where the ener the orm of heat. Each. convolution of the coil 9 possesses the same electrostatic capacity with respect to each and all the remaining convolutions. This property of the device arises from the coil being immersed in a body 'of electrolyte, as shown in Fig. 1

and, as a consequence, a multiplicity of resonant circuits is available in a single device.

The electrical equivalent of the device shown in Fig. 1 may, during complete breakdown of the film, be represented by the choke coil 90f Fig. 3 in which resistance elements 10 only are connected between adjacent convolutions of the coil. 1

In Fig. 1, the coil 1 may be considered as being embedded in the resistance material or electrol 2 which, when the resistance films upon t e coil are disrupted, serves as a means for dissi atin as heat, the ener y absorbed from t e disturbances. disturbance has been absorbed or its amplitude reduced to a suflicientl low value, the disrupted films upon the coi 1 are automatically reformed by reason of the pro erties possessed by the electrolyte 2. In t is instance, the protective device is automatically restoredto its original state without replacof the impulses will be dissipated in After t e ing any of the elements embodied in the structure. The character of the electrolyte 2 may be modified to increase or decrease its resistance properties.

It will be understood by those skilled in the art that embodiments of my invention, other than those shown and described, ma be made without departing from the spirit and scope of the appended claims.

I claim as my invention:.

1. A protective device comprising a loadcurrent-carrying inductance coil formed of a film-forming metal, and a body of electrolyte within which said coil is immersed.

2. A protective device comprising a. loadcurrent-carrying inductance coil of filmformin metal, and an electrolyte in contact with. the coil for forming resistance films on the exposed surfaces thereof.

3. A protective device comprising a loadcurrent-carrying inductance coil of ,filmforming metal, and an electrolyte in contact with the coil for formin high-resistance films on the exposed sur aces thereof and inserting resistance paths between adjacent resistance current-carrying inductance coil having ahigh-resistance film formed on the exposed surfaces thereof, and a body of electrolyte in which said coil is immersed and which serves to provide resistance shunt paths between ad acent convolutions of the coil for currents that are impeded in their flow throu h the coil.

6. protective device comprising a loadcurrent-carrying inductance coil' of fi1mforming metal, and a body of electrolyte for automatically reforming said films on the coil when they are disrupted, said electrolyte servirtig as energy-consuming means for impulses at are directed therethrough by the reactance of said coil.

7. A protective device comprising a loadcurrent-carrying inductance coil of filmformin metal, and abody of electrolyte in which t e coil is immersed, said electrol be being ca able of automatically reforming disrupte films on the coil and serving as energy-consuming means for electrical disturbances that disrupt the coil films.

8. A protective device com rising an inductive coil having a plurali y of convolutions, and -means providing the operative equivalent of condensive elements and resistors severally connected in parallel relaequivalent of condensive elements severally 15 tion between each convolution and each of connected to the convolutions of said coil the remaining convolutions. and jointly adapted to provide a parallel 9. A protective device comprising an inresonant circuit, 1n conpmction with porductive coil having a plurality of convolutions of said choke 0011, for each of a plutions, and means providing the operative rality of operating frequencies. 20

equivalent of condensive elements severally 11. A protective device comprising a norconnected to the convolutions of said coll mally ener ized current-carrying inductance and a common junction point and of resistcoil forme of a film-forming metal, and a ors severally connected in shunt relationto body of electrolyte within which said coil said apparent condensive elements. is immersed. 25

10. A protective device comprising an in- In testimony whereof I have hereunto subductive coil having a plurality of convoluscribed my mama this 8th day of March 1917. tions, and means providing the operative CHARLES LE G. FORTESGUE. 

